The invention relates to a double-cylinder two-stage compression rotary compressor, and more particularly to a double-cylinder two-stage compression rotary compressor which can adequately prevent leakage of refrigerant gas from the sealing of two compressors separated by an intermediate partition panel.
Generally, a double-cylinder two-stage compression rotary compressor is accommodated in an enclosed container together with an electric motor connected with the rotary compressor by a common rotary shaft.
The rotary compressor comprises first and second cylinders for compressing a refrigerant gas, in two stages, to a first (intermediate) pressure by the first compressor and to a second (higher) pressure by the second compressor. The first and the second cylinders are separated by an intermediate partition panel. Associated with the first and the second cylinders, there are two eccentric members one for each cylinder, which are mounted on the rotary shaft and offset from each other in phase by 180xc2x0. Mounted on the respective eccentric members are annular rollers which are adapted to roll on the inner walls of the respective cylinders. The intermediate partition panel has a bore whose diameter is a little larger than the rotational diameter of the eccentric members or the inner diameter of the rollers.
As the rotary shaft rotates, the first roller rotates eccentrically in the first cylinder to take the refrigerant gas thereinto, compress it to an intermediate pressure, and discharges it. The elements participating in this compression constitute a first (stage) compressor. The compressed gas pressurized to this intermediate pressure is further pressurized by the eccentric rotation of the second roller in the second cylinder. These elements participating in the second compression constitutes a second (stage) compressor.
In a double-cylinder two stage compression rotary compressor where the pressures inside the rollers of the respective cylinders and in the bore of the intermediate partition panel are allowed to equilibrate with the pressure in the sealed container of the compressor, leakage of the refrigerant gas takes place between the insides of the rollers and the compression spaces (or suction spaces) in the cylinders, which leakage depends on the pressure difference across the roller end clearance and the width of the sealing areas between the rollers and the intermediate partition panel.
In a typical compressor, the bore of the intermediate partition panel is coaxial with the rotary shaft, for which the minimum roller end clearance is defined by a formula below.
Minimum roller end clearance (width)=[(outer diameter of a roller)+(eccentricityxc3x972)xe2x88x92(shaft diameter+eccentricityxc3x972+xcex1)]/2where shaft diameter+eccentricityxc3x972=shaft pin diameter.
In assembling the shaft, the bore of the intermediate partition panel must have an allowance a for allowing smooth passage of the shaft.
Since minimum roller end clearances,always exist on the opposite ends of each eccentric member, such prior art compressor suffers from the leakage of the refrigerant gas through the clearances, i.e. through spaces on the opposite ends of the eccentric members, due to the pressure difference between them, thereby degrading the volumetric efficiency and the compression efficiency of the compressor.
It is therefore a primary object of the invention to overcome above mentioned prior art problems by providing a double-cylinder two-stage compression rotary compressor equipped with an intermediate partition panel having a bore suitably configured to minimize the leakage of the refrigerant gas from the compressors, thereby attaining an improved volumetric efficiency and a compression efficiency and hence a large refrigeration performance, irrespective of whether the sealed container is designed to receive a higher, low, or an intermediate pressure gas.
In one aspect of the invention, there is provided a double-cylinder two-stage compression rotary compressor comprising:
a sealed container;
an electric motor accommodated in the sealed container;
first and second eccentric cams mounted on the shaft of the motor;
first and second rollers rotatably fitted on the respective first and second eccentric cams;
first and second cylinders in which the first and second rollers are rolled on the respective inner walls of the cylinders when driven by the shaft;
an intermediate partition panel having a central bore and separating the first and second cylinders;
first and second support members sandwiching the first and second cylinders to form first and second spaces each defined by the intermediate partition panel, the respective roller and cylinder;
first and second vanes, the first vane partitioning the first space into a first suction space and a first discharge space, and the second vane partitioning the second space into a second suction space and a second discharge space;
first and second suction ports for taking a refrigeration gas into the suction spaces;
first and second discharge ports for discharging compressed refrigerant gas out of the discharge spaces, wherein
together with the intermediate partition panel and first support member, the first eccentric member, first roller, and first cylinder constitutes a first compressor driven by the shaft for compressing to an intermediate pressure in the first discharge space the refrigerant gas taken in the first suction space via the first suction port and for discharging the compressed refrigerant gas from the first discharge port;
together with the intermediate partition panel and second support member, the second eccentric member, second roller, and second cylinder constitutes a second compressor driven by the shaft for compressing to a high pressure in the second discharge space the refrigerant gas taken from first discharge port into the second suction space via the second suction port and for discharging the compressed refrigerant gas from the second discharge port, the rotary compressor characterized in that:
the refrigerant gas having the intermediate pressure is discharged into the container, allowing the container to have the intermediate pressure,
the center of the bore of the intermediate partition panel facing the first compressor is offset away from the center of the shaft to an angular position having a central angle about the center of the shaft in the range of 270-360 degrees with reference to the vane (0 degree); and
the center of the bore of the intermediate partition panel facing the second compressor is offset away from the center of the shaft to an angular position having a central angle about the center of the shaft in the range of 90xc2x145 degrees with reference to the vane (0 degree).
By increasing the sealing area of each roller in sliding contact with the intermediate partition panel, across which a pressure difference is generated, sealability of the area can be improved.
The bore of the intermediate partition panel may be a two-step bore having first and second bores offset to each other.
The intermediate partition panel may be formed of a first partition panel facing the first compressor and having a first bore, and a second partition panel facing the second compressor and having a second bore.
The entire partition panel may be fabricated from a single plate by forming an inclined bore.
In a case where the high pressure refrigerant gas is released from the compressor into the sealed container, making the pressure high therein, the center of the bore of the intermediate partition panel is preferably offset away from the center of the shaft to an angular position having a central angle about the center of the shaft in the range of 270-360 degrees with reference to the vane (0 degree).
If, on the other hand, a low pressure refrigerant gas is released from the compressor into the sealed container, making the pressure low therein, the center of the bore of the intermediate partition panel is preferably offset away from the center of the shaft to an angular position having a central angle about the center of the shaft in the range of 90xc2x145 degrees with reference to the vane (0 degree).